The use of surfactants as adjuvants for enhancing herbicide uptake is known. Detailed discussions of the use of surfactants in agrochemical formulations are described in Surfactants in Agrochemicals, Tharwat F. Tadros, Marcel Decker, Inc. Surfactant Science Series, 1995 and Adjuvants for Herbicides, Weed Science Society of America, 1982, both publications incorporated by reference herein.
Further, U.S. Pat. No. 4,931,080, issued Jun. 5, 1990 to Chan and U.S. Pat. No. 5,047,079, issued Sep. 10, 1991 to Djafar et al, both disclose solid weed killing compositions comprising N-phos-phonomethyl-N-carboxymethyl herbicides and nonionic surfactants such as PLURONIC.RTM. surfactants which are EO/PO block copolymers. In U.S. Pat. No. 5,104,647, issued Apr. 14, 1992, Policello discloses a surfactant blend comprising an organosilicone compound and a polyalkylene oxide copolymer, such as PLURONIC.RTM. surfactant, useful as an agricultural adjuvant. Finally, U.S. Pat. No. 5,187,191, issued Feb. 16, 1993 to Otten et al, discloses physically stable aqueous pesticide compositions comprising water insoluble pesticides, polyoxyalkylene copolymer and water. Said polyoxyalkylene copolymer is heteric, i.e. it is comprised of EO and PO units, wherein some PO is incorporated into the EO blocks, e.g. (EO/PO) (PO) (EO/PO), in order to provide a liquid surfactant which is more easily used than a paste.
However, the use of these liquid heteric EO/PO block copolymers as adjuvants to increase the uptake of herbicides has not been described. Prior to the invention described herein, non-heteric EO/PO blocks with higher amounts of EO (i.e. &gt;30%) had not been previously tested in tank mixes because their physical form (paste) rendered them impractical for this application.
Applicants have now surprisingly discovered that liquid heteric EO/PO block copolymers, wherein the EO content is at least 30% by weight, are useful for enhancing the efficacy of herbicides and, thus, enhancing weed controlling activity.